1. Field of the Invention
This invention pertains to an interface to convert an input analog video signal (real-time) into an output to drive a matrix of light-emitting-diodes wherein the buffers use random access input in accordance with the physical and data format of the display and direct memory access output. One of a pair of buffers receives data by random access so that the data is arranged in the order or sequence in which the output is desired while the other of the pair of buffers outputs data by direct memory access, then the functions reverse. This parallel-like structure and memory technique eliminates the need for separate input and display RAMs.
2. Description of the Prior Art
The use of a multi-color light-emitting-diode (LED) matrix to display moving video-type images is well-known in the prior art. However, prior art displays are limited by the size of image which can be digitally stored in random-access-memory. For example, for a 640 by 400 element LED matrix, with each element displaying three colors at sixteen intensity levels, twelve bits of storage are required for each of the 256,000 pixels being displayed. If this picture were stored in RAM, a one-minute presentation would require 5.53 billion bits of storage if the frames changed only thirty times per second. This is an unrealistic amount of storage, at least in random-access-memory. However, massive read-write analog storage of video signals is economically available from videotape and similar media. Similarly, it may be desirable, in real-time, to convert an input analog video signal (such as an input to a television or a personal computer screen) into a digital signal to drive an LED display matrix. It is desirable for such an apparatus to be easily adaptable to various sizes of LED display matrices and to various input requirements configurations.
While the same result has been achieved by television studio apparatus, the television studio apparatus requires very fast components (well in excess of 40 megahertz). This has made the prior art equipment very expensive.
Additionally, some proposed prior art solutions, such as U.S. Pat. No. 5,184,114 to Brown have relied on the use of separate input and display RAMs with data distributed or parsed out from the input to the display RAMs using a shift register approach. Such devices may be difficult to implement satisfactorily due to fundamental constraints with regard to speed, synchronization and matrix size.
Additionally, some primitive prior art used color sequential output and did not provide for the simultaneous display of colors. Additionally, this primitive prior art was limited to the display of two intensity levels for each pixel. That is, the colors within a pixel could not have their color intensity changed individually.